An inkjet recording method has been widely used because of advantages such that full-color recording is easily achieved as the process thereof is simple compared to other recording method, and images of high resolution can be attained even with a device of a simple structure.
As an inkjet ink, a dye ink and a pigment ink are available. In the case of an aqueous pigment ink, a surfactant or water-soluble resin is generally used for dispersing a hydrophobic pigment. Moreover, there have been known the technique such that film-forming resin particles are added for improving an image quality, and the technique (Patent Literature 1) such that a wetting agent (e.g. glycerin and polyhydric alcohol) is added for improving jetting stability. However, it is difficult to stably and finely disperse numbers of substances, and the degradation of the stability of ink due to the long-period of storage is especially problematic.
Moreover, Patent Literature 2 discloses an ink containing a compound which contains trimethylglycine and is represented by the general formula (I), and at least one water-soluble compound selected from the group consisting of the (nitrogen-containing) compound represented by the general formula (II), polyalkylene glycol, polyglycerin, and bishydroxyethylsulfone, and lists 1,5-pentane diol, 1,6-hexane diol, and the like as a water-soluble compound usable in combination. However, the combination of trimethylglycine and C4-6 diol, and the usability thereof are not mentioned therein.